Here are the answers to the questions:
Part A The side length of cube A is 1 inch.
Part B The volume of cube A is 1 inch x 1 inch x 1 inch = 1 cubic inch.
Part C The side length of cube B is 3 inches.
Part D The volume of cube B is 3 inches x 3 inches x 3 inches = 27 cubic inches. To fill cube B with cubes identical to cube A, you need 27 cubes of 1 cubic inch each. This is because 27 cubic inches / 1 cubic inch = 27.